<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  
  <script>
    class Person {

      constructor(name, age) {
        this.name = name
        this.age = age
      }

      running() {
        console.log('running');
      }
    }

    class Student extends Person {
      constructor(name, age, tel) {
        super(name, age)
        this.tel = tel
      }
    }

    const stu = new Student('大头', 18, 17712345678)
    console.log(stu, stu.tel);
    stu.running()
  </script>
</body>
</html>